Air seeders typically include an implement frame mounted on wheels, with a plurality of furrow openers mounted on the frame. The furrow openers can be moved from a raised non-operative position to a lowered operating position where the furrow openers engage the ground and create furrows. Agricultural products such as seed and various types of fertilizer are carried in separate tanks which can be mounted on the implement frame or on a cart towed along with the implement frame.
The application rate of the various products varies significantly from as low as about three pounds per acre to 300 pounds per acre or more. In order to keep track of the amount of product remaining in each tank it is known to provide sight glasses or low level alarms to measure product remaining in the tank, or at least warn when a tank is approaching empty. Cameras are also sometimes used in the tank so the operator can visually monitor the product quantity, and it is further known to mount load cells under a tank and provide a readout of the weight of product in the tank. Present product containers for air seeders however, are typically are built with a number of compartments in a single tank assembly. The assembly thus contains a number of tanks separated by walls, and it is thus not possible to weigh the product in each tank, but only the entire tank assembly.
Metering devices dispense products from the tanks into one or more air streams that carry the products through a network of hoses and manifolds to the furrow openers where same are deposited in the furrows. Most modern air seeders have furrow openers that deliver seed to seed furrows and fertilizer to separate fertilizer furrows. These may be totally separate furrow openers mounted on separate shanks, such as mid row fertilizer banding furrow openers which are remote from the seed furrow openers, or combination furrow opener where a single shank supports a furrow opening tool that makes one furrow for seed and a separate furrow for fertilizer. There are also then two separate distribution networks, one delivering product from selected ones of the tanks to the seed furrows, and one delivering product from selected ones of the tanks to the fertilizer furrows.
The terms “seed” and “fertilizer” are not meant restrictively, since in many cases some fertilizer is metered into the air stream carry the seed, and also in some instances it may be that fertilizer may be directed into the “seed” furrows, and vice versa if conditions warrant it. The terms “seed” and “fertilizer” are simply convenient to differentiate the two separate “runs” or air streams. Basically in an air seeder it is desirable to be able to direct agricultural product from any of the tanks into any of the available air streams.
The wide range of application rates applies not just to total product but also to the product mix. When seeding canola for example the application rate of canola seed may be three pounds per acre while fertilizer is applied at 300 pounds per acre. It is desirable then to use a smaller product tank for canola seed, and direct the seed from that tank to the seed air stream for carriage to the seed furrows. On the other hand when seeding peas for example the application rate of pea seed may be 200 pounds per acre while fertilizer is applied at 50 pounds per acre, and it is then desirable to use one or more larger product tanks for pea seed, and direct the seed from those tanks to the seed air stream for carriage to the seed furrows. Thus the frequency of the need to stop and fill when one tank is empty can be reduced.
In a typical air seeder a metering roller, auger, or the like dispenses product from each tank into an air stream. A conduit or the like generally connects the air stream to the top of the interior of the tank to pressurize the tank so that there is no pressure differential between the tank and the air stream which would put back pressure on the product as it is being metered into the air stream. This requires that the lid on the tank fill opening is sealed and clamped when closed.
The air stream carries the product through a primary hose to a manifold where the air stream and product is divided and directed into multiple secondary hoses connected to the manifold outlet ports. In some arrangements each secondary hose connects into a further manifold and the air stream is divided again into further final hoses leading to each furrow opener. It is desired to have an equal product quantity in each of the secondary hoses to provide equal product quantity in each of the final hoses, however the secondary and final hoses are typically of varied lengths. A longer hose will exert more back pressure and resistance to flow from the manifold compared to a shorter hose, and so air and product flows from the manifold are unequal as the longer hoses have a reduced flow and the shorter hoses have increased flow. In addition, manifolds of various sizes are also often used on one air seeder, for example some of the manifolds may have six outlets, and some eight outlets, to conveniently match the number of openers on the air seeder. As a result different pressures in the different sized manifolds again contribute to uneven distribution to the furrow openers.
Wider air seeders require more furrow openers and therefore more manifolds. Thus it is also known to divide product by delivering product from different sections along the length of a continuous meter roller into different air streams in different primary hoses, and then into manifolds. With this system, it is desirable to have the air pressure at the metering area to be the same for all primary hoses, so that reverse air flow through the meter won't affect the metered rate in one primary hose compared to another. To help achieve this balanced pressure all primary hoses are typically the same length.
Dividing at the meter roller reduces the number of manifolds required, but with a continuous meter roller divided into sections, sealing between sections is problematic and air and product can cross over from one meter section to another section, reducing the desired uniformity of metered product distribution to each opener.
In order to reduce overlap in very wide air seeders it is further desirable to be able shut off the supply of product to sections of the air seeder. It is known to use gate mechanisms for shutting off flow of product from the tank to a section of a continuous meter roller however these gate type shut off mechanisms result in product flow on/off lead times that are difficult to deal with. The product between the gate and the meter roller continues to be metered until it is used up, even after the gate is closed. For products that are metered at a low rate, it takes a significant time for the product to stop flowing to the furrow openers. Again for these products, when the gate is re-opened it takes some time for the meter to turn enough to start dropping product into the air stream. Such a gated meter is disclosed for example in U.S. Pat. No. 7,690,440 to Dean.
In some air distribution systems gate mechanics are also used to direct the product from one metering device to either the seed air stream or the fertilizer air stream. Again sealing such gates is difficult and air can pass between the seed and fertilizer air streams, especially when the speed and pressure of one air stream is significantly greater than the other. When seeding low rates of light seed like canola, it is desirable to have a low air speed and pressure, while often at the same time it is desired to apply a high rate of fertilizer which requires a high air speed and pressure to carry the high product volume through the system. When two different pressures and air speeds enter such a gated meter system, the air crosses over from the fertilizer to the seed side resulting in increased air speed on the seed air stream and reduced air speed in the fertilizer air stream.